Hi Steve and Linda, I just started reading your Mariner’s Weather Handbook and I stumbled across something on page 59. In the italic at the bottom of the page it is stated that the effect of coriolis is less at higher altitude. I was puzzled by this, because from my time as an aviation student (a long, long, 21 years ago) I remembered that, due to friction, the effect of coriolis close to the surface, and especially over land, was less. Also in the italic part you (correctly I believe) state that over water (less friction) the wind angle relative to the isobars is less. This indicated a greater effect of coriolis. With no coriolis at all the wind angle would be perpendicular to the isobars. This also agrees with my experience as a pilot. The first 4000ft or so the wind veers as you go up. Less friction means greater effect from coriolis. What do you think? Has 21 years been too long or is there indeed something unclear in the text, and is it that what has got me thinking? I would very much appreciate it if you could shed some light on this matter. In the meantime I’ll continue reading your fine book, as I’ve done with the Offshore Cruising Encyclopedia.
Hi Jos: I think you may be confusing “wind shear” with Coriolis from a flying standpoint. I fly gliders, and we are always very concerned with shear if we are landing. Shear is very much a friction issue and the closer you get to the ground the less wind you will have. I re-read the italicized caption at the bottom of page 59 and I think it is correct. The easiest way to visualize how this works is to consider the difference in direction between surface winds and low cloud levels. Surface winds are angled inwards from the isobars around lows and outward around highs. This is due to Coriolis. However, the clouds aloft typically follow the isobars, that is, they do not show effects of Coriolis so they are not angled in or out for highs and lows–one other issue which may be confusing you from your flying. When there is a lot of shear around on landing there is typically a significant wind shift associated with it. Hope this helps out.
Posted by Steve Dashew (November 30, 1999)
